全文获取类型
收费全文 | 457篇 |
免费 | 134篇 |
国内免费 | 127篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 69篇 |
地球物理 | 290篇 |
地质学 | 189篇 |
海洋学 | 22篇 |
天文学 | 90篇 |
综合类 | 32篇 |
自然地理 | 14篇 |
出版年
2016年 | 1篇 |
2015年 | 9篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 76篇 |
2010年 | 48篇 |
2009年 | 74篇 |
2008年 | 11篇 |
2007年 | 29篇 |
2006年 | 35篇 |
2005年 | 59篇 |
2004年 | 146篇 |
2003年 | 35篇 |
2002年 | 29篇 |
2001年 | 24篇 |
2000年 | 32篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1950年 | 2篇 |
1949年 | 1篇 |
1943年 | 1篇 |
1940年 | 1篇 |
1937年 | 4篇 |
1934年 | 2篇 |
1933年 | 9篇 |
1928年 | 1篇 |
1927年 | 2篇 |
1926年 | 1篇 |
1924年 | 6篇 |
1923年 | 2篇 |
排序方式: 共有718条查询结果,搜索用时 109 毫秒
101.
Experiments on ion implantation were performed in order to better characterize diffusion of noble gases in lunar soil.4He+ at 50 keV with 5×1016 ions/cm2 was implanted into lunar simulants and crystal ilmenite.Helium in the samples was released by stepwise heating experiments.Based on the data,we calculated the helium diffusion coefficient and activation energy.Lunar simulants display similar 4He release patterns in curve shape as lunar soil,but release temperatures are a little lower.This is probably a con... 相似文献
102.
基于高空间分辨率的红树林卫星遥感监测技术进展 总被引:1,自引:0,他引:1
卫星遥感技术是红树林生态系统监测的重要手段。文章系统地总结了红树林的光谱特征,给出了目前应用于红树林生态监测的高空间分辨率卫星包括IRS-P6、SPOT-5、IKONOS、OrbView-3、QuickBird的主要技术参数以及它们在红树林遥感监测中的应用程度,叙述了目视解译法、波段组合法、图像分类法、专家分类法、模糊分类法和面向对象分类法等遥感监测技术方法在红树林的生态参数包括类外区分和类内区分、生物量和健康状况等的遥感提取的应用和精度对比情况。另外,对应用高分辨率卫星遥感资料监测红树林的技术发展趋势进行了讨论。 相似文献
103.
Peijian Shi Jie Liu Zhen Yang Agricultural College Jiangxi Agricultural University Nanchang China China Earthquake Networks Center Beijing China 《地震学报(英文版)》2009,(3):231-237
For exploring the aftershock occurrence process of the 2008 Wenchuan strong earthquake, the spatio-temporal point pattern analysis method is employed to study the sequences of aftershocks with magnitude M≥4.0, M≥4.5, and M≥5.0. It is found that these data exhibit the spatio-temporal clustering on a certain distance scale and on a certain time scale. In particular, the space-time interaction obviously strengthens when the distance is less than 60 km and the time is less than 260 h for the first two aftershoc... 相似文献
104.
Chuanyong Wu Jun Shen Jun Li Zhiyong Xiang Jun Hu Yili Ya'er Earthquake Administration of Xinjiang Uygur Autonomous Region Urumqi China 《地震学报(英文版)》2009,(1):69-74
We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi,and an integrated analysis in conjunction with data of deep seismic sounding.Our result suggests that under the SN-oriented compressive stress,the Xishan block moves steadily toward the Tianshan Mountains in south,resulting in southward thrust-slip and crustal shortening,particularly the southward thrust of the Xishan fault which serves as the main boundary in south.North of the Xishan fault are the ... 相似文献
105.
Ying Li Jianguo Du Fukuan Wang Xiaocheng Zhou Xiaodong Pan Ruqing Wei Institute of Earthquake Science China Earthquake Administration Beijing China Inner Mongolia Corporation Ltd.of Geologic Engineering Hohhot China Earthquake Administration of Jilin Province Changchun China Liaocheng Seismology Hydro-chemistry Test Station Liaocheng China 《地震学报(英文版)》2009,(1):93-100
The geochemical backgrounds and origins of soil gases in the Yanhuai basin are discussed based on the regional seismogeological data and concentrations of Rn,Hg,CO2,H2,He and CH4 in soil gas measured at 422 investigating sites in field during September to October 2007.The geochemical background values of Rn,Hg,CO2,H2,He and CH4 are(8105.8±5937.4) Bq/m3,(9.7±5.8) ng/m3,(395.9±35.3)×10-6,(4.0±2.3)×10-6,(15.9±10.4)×10-6 and(12.7±8.1)×10-6,respectively.The geochemical backgrounds of the soil gases are higher in... 相似文献
106.
Xiaoqing Wang Xiang Ding Long Wang Yan Wang Institute of Earthquake Science China Earthquake Administration Beijing China 《地震学报(英文版)》2009,(2):129-133
The paper introduces firstly the seismic loss assessment method based on macro-economic indicators and new vulnerability models determined by the data from the on-site damage and loss survey to earthquakes occurred in China during the last two decades.The fast assessment for the 2008 Wenchuan earthquake with MS8.0 is given based on an empirical intensity attenuation relationship.Compared with the assessment based on the practical seismic intensity map of the event according to the on-site investigation, the... 相似文献
107.
Ground motion attenuation relations of small and moderate earthquakes in Sichuan region 总被引:1,自引:0,他引:1
Lanchi Kang Xing Jin Fuzhou University Fuzhou China Earthquake Administration of Fujian Province China 《地震学报(英文版)》2009,(3):277-282
On the basis of 10 935 broadband velocity records of 135 earthquakes (ML3.0-6.4 and epicentral distance of 26-623 km) occurred from May 12 to June 10 in 2008, which are collected from 27 bedrock stations included in Sichuan Earthquake Monitoring Network, the corresponding acceleration records are obtained by a real-time simulation method. Then by regression analysis on the data, the relation between the peak ground acceleration and velocity attenuation of small and moderate bedrock earthquakes occurred in S... 相似文献
108.
Chun Jiang Xueli Wei Xiaofeng Cui Dexiang You Earthquake Administration of Tianjin Municipality Tianjin China Tianjin University of Technology Tianjin China 《地震学报(英文版)》2009,(3):315-320
This paper introduces the method of support vector machine (SVM) into the field of synthetic earthquake pre-diction, which is a non-linear and complex seismogenic system. As an example, we apply this method to predict the largest annual magnitude for the North China area (30°E-42°E, 108°N-125°N) and the capital region (38°E-41.5°E, 114°N-120°N) on the basis of seismicity parameters and observed precursory data. The corresponding prediction rates for the North China area and the capital region are 64.1% and ... 相似文献
109.
Guoze Zhao Yan Zhan Lifeng Wang Jijun Wang Ji Tang Qibin Xiao Xiaobin Chen Institute of Geology China Earthquake Administration Beijing China 《地震学报(英文版)》2009,(4):395-402
Three experiments are carried out for earthquake monitoring using electromagnetic (EM) methods in recent years. Some earthquakes occurred in chance of the measurement time period for each experiment and the anomalies were recorded before the shocks. The observation at a site 20 km away from the epicenter of Zhangbei MS6.2 earthquake in 1998 shows that the apparent resistivity decreases in the strike direction before and/or during the earthquake and the resistivity increases in the de-cline direction. This a... 相似文献
110.
Jianping Wu Yuehong Ming Lihua Fang Weilai Wang Institute of Geophysics China Earthquake Administration Beijing China 《地震学报(英文版)》2009,(4):409-416
The S wave velocity structure in Changbaishan volcanic region was obtained from teleseismic receiver func-tion modeling. The results show that there exist distinct low velocity layers in crust in volcano area. Beneath WQD station near to the Tianchi caldera the low velocity layer at 8 km depth is 20 km thick with the lowest S-wave velocity about 2.2 km/s. At EDO station located 50 km north of Tianchi caldera,no obvious crustal low velocity layer is detected. In the volcanic re-gion,the thickness of crustal ... 相似文献